The present invention relates to the field of wireless communications, and, more specifically, to supporting an incoming call through a wireless gateway switch destined for a mobile subscriber unit.
Mobile wireless communications is rapidly becoming ubiquitous throughout the world. A major goal of all mobile wireless service providers is to provide seamless service so that wireless service, including incoming calls, is available to a mobile subscriber unit wherever it is currently located.
Because of this cooperation among service providers, a mobile subscriber unit can roam from a service area of a serving mobile switching center (MSC) to a service area of another MSC. To facilitate seamless roaming, the wireless system registers the location of the mobile subscriber unit as the mobile subscriber unit moves from place to place. Location information is typically stored in a home location register (HLR), which may be a stand-alone entity (stand-alone HLR) or may physically reside at a home MSC (integrated HLR). A xe2x80x9chome MSCxe2x80x9d for a mobile subscriber unit is the MSC that serves the location where the mobile subscriber unit is primarily located.
FIG. 1 illustrates an exemplary incoming call for a roaming wireless subscriber unit in wireless system according to the prior art ANSI-41 messaging. The incoming call is initiated when telephone 101 dials the directory number of wireless subscriber unit 108. The call is delivered to switching network 102 over facility 110. Switching network 102 directs the incoming call to wireless gateway switch 103 via facility 111. A xe2x80x9cwireless gatewayxe2x80x9d switch is a portal or point of entry for calls from a public switch telephone network, such as 102, to a wireless network. Wireless gateway switch 103 determines where mobile subscriber unit 108 is located by requesting HLR 104 for the location of mobile subscriber unit 108. In order to do so, wireless gateway switch 103 sends a location request message 112 to HLR 104. Message 112 contains the directory number of mobile subscriber unit 108 (DGTSDIAL field in the message). HLR 104 maintains a record that includes the location of mobile subscriber unit 108, comprising the serving MSC 105 in which mobile subscriber unit 108 has last registered. A visiting location register (VLR) 106 record is maintained at serving MSC 105 while mobile subscriber 108 is located within the region served by MSC 105.
In response to message 112, HLR 104 sends a route request message 114 to the serving MSC (105 in this example) where the mobile subscriber unit last registered. Message 114 contains an IMSI field, which designates mobile subscriber unit 108. Serving MSC 105 responds to HLR 104 with route request return result message 115, which contains an MSCID field and TLDN field. MSCID field identifies serving MSC 105 and is represented as a 24-bit digital number (with 16 bits representing the system identification and 8 bits representing the switch number) in accordance with ANSI-41. TLDN field is a temporary local directory number that is subsequently utilized in the call scenario for delivering the incoming call to serving MSC 105. HLR 104 conveys the information received in message 115 by sending location request return result message 113 (including MSCID field and TLDN field) to wireless gateway switch 103.
Wireless gateway switch 103 delivers the incoming call to serving MSC 105, as identified by MSCID field, over facility 117 designating a telephone number according to TLDN field. Serving MSC 105 continues the delivery of the call to a serving base station, in this example base station 107, in which mobile subscriber unit 108 is located. Radio communications is established between serving base station 107 and mobile subscriber unit 108 over radio channel 119, thus completing the call between telephone 101 and mobile subscriber unit 108. Other standards, such as GSM mandate similar call setup message traffic.
With all the messages sent from place to place to establish each incoming call, message traffic on the wireless system (typically SS7 in North America) is increased and call capacity is decreased. Also, because messaging is increased on a per call basis, the inherent time delay associated with call setup for an incoming call is increased. Moreover, TLDNs (for a wireless system complying with ANSI-41) and MRNs (for a wireless system complying with GSM-MAP) are required for completing the incoming call. If the number of TLDNs or MRNs that are assigned to a serving MSC is exhausted, the serving MSC cannot accept incoming calls until a TLDN or an MRN is relinquished from a previously established incoming call. In such a case, the service provider must either accept call blockage that is associated with the limited pool of TLDNs or MRNs or increase the size of the TLDN pool or MRN pool of the serving MSC""s. TLDNs and MRNs are typically valid telephone numbers that can be otherwise assigned to a local revenue producing mobile subscriber unit.
The present invention effects an economical call setup to a mobile subscriber unit located within a gateway cluster. The gateway cluster comprises a wireless gateway switch and at least one MSC. The wireless gateway switch identifies a facility to a serving MSC from a new data structure according to the present invention. If the serving MSC is not in the gateway cluster, a facility to the serving MSC is identified by a method or apparatus according to prior art.
The present invention obviates a route request message between an HLR and a serving MSC including the temporary telephone number. A wireless gateway switch queries the HLR about the location of the mobile subscriber unit. The wireless gateway switch chooses a facility to the serving MSC according to a relationship between the serving MSC identifier (MSCID) that is provided by the HLR and a facility identifier. The wireless gateway switch utilizes a data structure in order to determine the facility identifier. In an exemplary example of the present invention, the facility identifier comprises a trunk group number.
Moreover, the present invention may be extended to call scenarios in which secondary call treatment is provided. The invention supports provisioning either the HLR or the wireless gateway switch with an indicator associated with each serving MSC of the gateway cluster. The indicator signifies whether the serving MSC is within the gateway cluster. The HLR utilizes the indicator to determine whether to generate a route request message to the serving MSC according to prior art or to suppress the route request message according to the present invention.
The exemplary embodiment exploits the present invention in a wireless invention utilizing ANSI-41 messaging and can be extended to GSM-MAP messaging. The exemplary embodiment supports incoming calls to the mobile subscriber unit and may result in providing secondary call treatment if the mobile subscriber unit does not respond to paging. The conservation of assignable telephone numbers allows for an increased number of mobile subscriber units that can be supported in a wireless system. Obviating the necessity of the two messages for an incoming call ameliorates the limitations imposed by the factors discussed heretofore.